1. Field of the Invention
The present invention relates to an X-ray image diagnosing apparatus and a controlling method of that for displaying a plurality of X-ray images acquired in different positions.
2. Description of the Related Art
A known X-ray image diagnosing apparatus for acquiring an image of blood vessels in which contrast is enhanced using a contrast medium includes an X-ray source and an FPD or an I. I. equipped at both ends of a substantially C-shaped holder (C-arm), respectively, and an image processing unit. This X-ray image diagnosing apparatus is generally also referred to as an angiography apparatus, which allows diagnosis and treatment (medical treatment), such as insertion of a catheter into an object such as a patient by a doctor, and acquisition of an X-ray image.
One of examinations using the X-ray image diagnosing apparatus is a lower-extremity angiography examination. In the lower-extremity angiography examination, an image of the entire long and narrow image-acquisition region from the abdomen to the tiptoe is acquired while a contrast medium injected through a catheter proceeded to the abdominal aorta is traced. In the acquisition of an image of the entire image-acquisition region, the entire image cannot be acquired at a time, so that images of the entire image-acquisition region are acquired in several times. In this case, injecting the contrast medium every image-acquisition exerts a large burden on the patient. Therefore, a method for acquiring an image of the entire image-acquisition region from the abdomen to the tiptoe by one injection of the contrast medium was devised. When a proper quantity of contrast medium is injected, the part dyed with the contrast medium flows from the abdomen toward the tiptoe in the blood stream. The image-acquisition is repeated while the stream is traced.
There are two kinds of image-acquisition method, that is, bolus-chase angiography and stepping angiography. The mask images of the entire image-acquisition region are collected using either of the two kinds of image-acquisition method, and after a contrast medium is injected into the patient, the contrast images of the entire image-acquisition region are collected to execute a digital subtraction angiography (DSA). Then, the mask images and the contrast images are subjected to subtraction processing in which they are differentiated every image-acquisition position to generate difference images (DSA images). When the plurality of DSA images at the image-acquisition positions are bonded together, a long image that displays the entire image-acquisition region from the abdomen to the lower extremity in which all the blood vessels are drawn is generated.
As an art related to the present invention, Japanese Unexamined Patent Application Publication No. 2004-236910 is disclosed.
However, with this related art, if X-ray exposure is performed at a fixed frame rate, DSA images taken at a plurality of image-acquisition positions each include a portion that can be sufficiently checked (diagnosed) with one DSA image, which will increase the amount of X-ray exposure of the patient.
Moreover, in angiography of narrow blood vessels, such as those of a lower extremity, the narrow blood vessels are lost in the noise on the DSA images, thus sometimes making it difficult to view the running blood vessels.
Furthermore, it is necessary for the DSA to set (register) image-acquisition positions in advance, which is inefficient for the operator to execute X-ray diagnosis.